This application is directed to an elongated intravascular device for the occlusion of an arterial passageway by forming thrombus therein for therapeutic purposes and particularly to the treatment of arrhythmia.
A frequently used method for treating a patient's heart exhibiting arrhythmia includes the use of antiarrhythmic drugs such as sodium and calcium channel blockers or drugs which reduce the Beta-adrenergic activity. Other methods include the surgically sectioning the origin of the signals causing the arrhythmia or a conducting pathway for such signals. Lately, however, a frequently used method to terminate the arrhythmia is to destroy the heart tissue at the site from which the signals causing the arrhythmia originate or at a pathway through which such signals pass. The latter methods of destroying tissue at such a site include applying laser or radio frequency (RF) energy to the patient's endocardium at or close to the site from within the patient's left or right ventricle in order to destroy heart tissue involved with the arrhythmia and thereby terminate the irregular heart beat. For example, the average arrhythmogenic site consists of about 1.4 cm.sup.2 of endocardial tissue, whereas a re-entrant site might be much larger. Presently used RF ablation techniques produce lesions about 0.5 cm.sup.2 in diameter, so a number of lesions usually must be generated in order to completely ablate the area of interest. If the site is not accurately mapped or if there is difficulty in accurately placing the distal tip of the ablation device, much good tissue which is neither the cause of nor involved with the arrhythmia surrounding the site will be unnecessarily destroyed.
The prior ablation methods typically used elongated intravascular devices which are advanced through the patient's vasculature until the distal portion of the intravascular device is disposed within one of the patient's heart chambers with the ablating means such as an RF emitting electrode or the distal end of an laser delivering optical fiber in contact with the desired region of the patient's endocardium. While this procedure is now widely practiced, it is difficult to precisely position the distal ablation portion of the intravascular device at the desired location where the tissue causing or involved with the arrhythmia is to be destroyed.
What has been needed and heretofore unavailable is a method and system which quickly destroys tissue causing or involved with the but which does not destroy an excessive amount of uninvolved tissue adjacent to the site. The present invention satisfies these and other needs.